Modern electronic devices often include one or more integrated circuit chips, which perform different applications and may communicate with each other to exchange different signals. Normally, the integrated circuit chips are mounted on a special board that provide supply and power lines to the circuits and signal lines for data exchange between the different circuit chips. These boards, called circuit boards or also referred to as printed circuit boards, may comprise one or more layers including one or more power and transmission lines. As the number of integrated circuit chips per board and the amount of a data communicated between these chips continues to increase, the number of layers of circuit boards also rises up. For example, modern circuit boards may comprise 4, 6, 10 or even more different layers.
Typically, such circuit boards can be used for different applications. For example, a motherboard of a computer system includes integrated circuit chips used for controlling the memory interface and input/output interfaces such as, i.e., USB, parallel and serial interfaces, as well as network devices such as, i.e., Ethernet or IEEE 801.11. A further example for a circuit board is a memory module, comprising a number of memory chips, i.e., RAM, ROM, Flash or EPROM memory. The memory chips are mounted on the board and connected to a contact bank of the module.
However, as the signal processing of the integrated circuit chips increase, electromagnetic emission radiated by the transmission or power lines within the circuit board may become an issue. Such emission, as seen in FIG. 5, is radiated as electromagnetic energy in each direction. The unintentional generation and propagation of energy can be received by a second device, thereby interfering with the device and causing unwanted effects. Such process is called EMI for electromagnetic interference. Consequently, countermeasures should be taken in order to avoid the propagation of such energy towards the external environment. Hence, there is a need for suppressing the emission of unwanted electromagnetic energy from a circuit board.